Commonly-owned U.S. Pat. No. 8,224,507 to Edwards, et al. (the “Edwards patent”), whose contents are incorporated herein in their entirety by this reference, identifies rationales for improving information available to pilots of, for example, soon-to-land aircraft as to conditions likely to be encountered upon landing. Arguably the most famous recent circumstance in which lives were lost because of inadequate information about landing conditions delivered to a flight crew is the crash of Southwest Airlines Flight No. 1248 on Dec. 8, 2005, which flight departed the end of a runway and left the airfield boundary at Midway International Airport in Chicago, Ill. Quoting the USA Today newspaper, the Edwards patent states:
. . . the pilots “assumed the runway was in ‘fair’ condition, based on reports from other pilots radioed to them by air traffic controllers.” However, subsequent analysis of objective data “show[ed] the conditions were ‘poor’ at best,” with the runway “so slippery that it would have been difficult for people to walk on, providing minimal traction for the jet's tires as pilots tried to slow down.”
See Edwards patent, col. 2, 11. 22-29.
The reason the pilots reporting those “fair” conditions had no manner of discerning their actual brake system performance was because the information about those systems was not designed to be measured, nor was it designed to be delivered to the flight crews. It is essentially impossible for pilots to discriminate between the aerodynamic forces acting upon an aircraft and the ground-based braking forces during a landing. As a result, the risks associated with poor ground-based braking system performance are not visible to a pilot in the act of directing his aircraft during such a maneuver.
Accordingly, detailed in the Edwards patent are systems and methods of improving or increasing (or both) the information available to operators in these and other circumstances. In some systems disclosed in the Edwards patent, objective information relating to performance of one aircraft using a runway is transmitted to an aircraft scheduled next or soon to use the runway for evaluation by the operator of that aircraft. Among many advantages of these systems are that they provide more objective information than conventional reports (which may consist of as little as a qualitative assessment of “good,” “fair,” or “poor”), the information may be provided in real-time (or near real-time), and the information may be generated without closing a runway to conduct conventional mechanical, ground-based friction testing.
Certain systems of the Edwards patent contemplate providing a vehicle operator with information relating to both (A) brake pressure commanded by an operator of an aircraft upon landing on a runway and (B) brake pressure delivered to the brakes of the aircraft after anti-skid control computer calculations are performed on-board that aircraft. Although other information may be provided additionally or alternatively, recently-obtained commanded and delivered brake pressure information may be especially valuable to operators of soon-to-land aircraft, as the information relates directly to what the operators will imminently experience. It thus may differ from the information most desired by engineers or regulatory authorities, for example, tasked with after-the-fact evaluation of runway conditions or an engineering analysis of aircraft performance.
Indeed, while humans are not considered “machines,” they do operate under industry recognized cognitive limitations when in the process of interacting with mechanical devices. This relationship between the performance of a human and how that affects the performance of a machine is known as the field of “human factors” study. Recognizing human limitations and creating communication paths between vehicle and operator likely to overcome the limitations is thus a useful and significant goal.
As suggested by the accident at Midway Airport (among other events), unexpected degradation in ground-based deceleration systems can drastically erode safety and lead to catastrophic consequences any time a vehicle is decelerating on a surface while employing both aerodynamic and ground-based deceleration systems. For a landing aircraft, the operator must employ muscle memory techniques for engaging ailerons, rudder, elevator, and throttle while simultaneously directing his vision to the designated operating runway. While travelling down the surface of a runway and in controlling both lateral movement and longitudinal movement of the aircraft, the pilot or operator currently has no automated method of alert (other than his own qualitative “feeling”) to queue an alternate sequence of actions should degraded system performance make such a decision advisable.
More specifically, a human operator of a decelerating aircraft must simultaneously control three dimensions of movement. In addition to controlling lateral and longitudinal movement of the aircraft, prior to contact with the ground he must align the flight path of the vehicle with the orientation of the surface on which he is to decelerate. This act requires the use of both feet and both hands to operate the rudder, ailerons, elevator, and throttle(s) of the aircraft. Meanwhile, the pilot's vision must be focused outside so that a continuous and speedy feedback loop develops between his visual cues and the actions of his hands and feet.
All landings involving human manipulation of controls are “visual” landings even though automation and navigational instruments may have delivered a craft to a position where such an event can take place. To this degree all such events require an operator of a craft to utilize a field of view designed specifically for viewing the environment outside the cabin or cockpit of the vehicle. However, the human mind is limited in its ability to process concurrent information at a conscious level of awareness. Attention is the cognitive mechanism in which an individual selects and processes important information while filtering and ignoring irrelevant information. Many factors can affect attention ranging from the physiological effects of stress to recognized cognitive limitations of the human brain. The concept of the “attentional blink,” for instance, represents the inability to identify the second of two targets when the two are presented in close temporal succession or rapid sequence. This represents a long-lasting attentional deficit that is due to the length of time an identified object occupies attentional capacity, or remains in the person's awareness. In this case, this attentional deficit can mask important real-time deceleration system performance since current aircraft are not designed to display alerts or warnings of this nature in the visual field of view used for landing. Studies have documented, however, that perceptual, spatial and temporal cues have been found to be effective in manipulating attention during periods in which attentional blink is most likely to exist. This is but one example of a range of human factors issues that can create barriers to the effective human integration with aircraft systems designed to produce a ground deceleration during the landing maneuver.
The science of procedural memory teaches that the cognitive limitations of a pilot will not allow him to perform more than one analytical function at a time. Functions that require more than one action are employed using muscle memory as developed through repetition and training. Procedural memory is memory for how to do something. It usually resides just below a person's conscious awareness and guides the processes humans perform such as when tying shoes, riding a bicycle, or landing an airplane. Procedural memories are used without the need for conscious control or attention. For a pilot landing an airplane, the continuous analysis of where the direction his flight and ground path take him becomes his sole focus. In the study of human factors he is said to be “task saturated” because the task of controlling the flight path of the vehicle maximizes his abilities of perception and analysis at a certain level of awareness. He therefore must rely on procedural skill to accomplish any other demands he may encounter.
To acquire a procedural skill, one must pass through three phases. The first is the “cognitive” phase, which is when attention is most significant. It is the time when a person organizes and understands how parts come together as a whole. The second phase is the “associative” phase, which involves repeating the practice until patterns emerge and the skill is learned. Important stimuli are incorporated and irrelevant information is dropped, so the ability to differentiate the two is important for perfecting the skill. The third phase is the “autonomous” phase, which involves perfecting the skill so that it seems automatic. The ability to discriminate important from irrelevant information is quicker, more accurate, and requires less thought process.
The landing environment, in which a pilot is focused on using visual cues to operate the aircraft systems, relies entirely on this autonomous phase of memory. Without a cue, or signal, to do things differently due to deteriorating conditions, a pilot or operator will continue with procedural memory despite an unfavorable outcome. By contrast, a cue could provide a signal to alert and redirect the pilot's attention to implement a different set of procedural memories.
Furthermore, decisions concerning what actions are appropriate (“go around” or “continue,” for example) are analyzed prior to the event so the operator need only be alerted to an expected cue to make an immediate assessment of his actions and continued techniques. This environment is classified as a “task saturated” one because there are so many actions taking place that there is very little room to employ a human function that relies upon anything but the simplest of cognitive alerts. This is an area where the possibility of errors due to perception and technique are greatly increased and where integration of man to machine is most important. It is also the state in which a pilot's vision is entirely dedicated outside the aircraft, away from his cockpit instruments.
Eye direction normally coincides with attention; however, research regarding the human detection of signals indicates that the mind processes more information peripherally than thought possible. As attention is directed across a person's field of vision (centrally and peripherally), items falling within what is referred to as the “attention spotlight” will be preferentially received, regardless of eye direction. In other words, humans can attend to something without looking directly at it, as long as it lies within the field of view being utilized.
Human visual cognition is particularly acute when a changing light source occurs within the peripheral vision of the operator. That changing light source can be either a flashing color or an alternating color(s), for example, and may (but need not necessarily) incorporate an alternating “wig wag” alert using one color or alternating two colors in the same display. Since the field of view of the pilot or operator is limited to the forward visibility above the instrument glare shield during a ground deceleration maneuver, placing a cueing or alerting device in this area would beneficially capture the operator's peripheral vision. Alternatively or additionally, including an aural alert may be advantageous.
Research performed regarding high task-loaded environments such as this indicates that the response to an alert must by necessity be a binary one, meaning that an alternate technique constituting a pre-learned muscle memory sequence is the only plausible consequence of an alert occurring during this phase of operation. Such a muscle memory response would include the necessary manipulation of the controls required to properly configure the vehicle for maximum effective deceleration and control.
Finally, the concept of “safety” is in effect the state in which exposure to risk is reduced to an acceptable level. “Risk” may be defined as the likelihood that a hazard relating to ground deceleration will result in an unwanted outcome that may produce harm to property, people, or both property and people. To have a “safe” system it is necessary to articulate the details that make up any given hazard. For the purposes of an aircraft decelerating on the surface, these hazards may include (but are not limited to) a difference between commanded and delivered wheel brake forces as the result of the actions of an anti-skid system (as noted above), the failure of a spoiler system to apply downward forces to a wheel brake system, degraded or absence of thrust reverser forces, a braking performance significantly different than selected by an automatic braking system, a failure of a pneumatic tire, the failure of a braking force delivery system such as hydraulics, or a tire to ground interaction for which an anti-skid system significantly reduces delivered braking forces. When these hazards occur during the time when a vehicle is travelling on a surface for the purpose of decelerating, the pilot flying currently has no indication of the hazards within the field of view he must use to control his vehicle while utilizing the muscle memory techniques as described above. The issue is sufficiently acute in connection with unrecognized deactivation of speedbrakes on aircraft that the National Transportation Safety Board recently recommended that warning horns be installed on jetliners to alert pilots if the speedbrakes cease functioning.